Mcs table adaptation for 256-qam

ABSTRACT

The present invention relates to adaptive modulation and coding scheme selection and signaling in a communication system. In particular, a modulation and coding scheme to be used for transmission of a data is selected from a set of predetermined modulation and coding schemes. The predetermination of the set is performed by selecting the set from a plurality of predefined sets. The sets have the same size, so that a modulation and coding selection indicator signaled to select the modulation and coding scheme may be advantageously applied to any of the selected sets. Moreover, a second set includes schemes with a modulation not covered by the schemes of a first set, and which is of a higher order than any modulation in the first set.

FIELD OF THE INVENTION

The invention relates to methods for transmitting and receiving data ina multicarrier communication system and, in particular, to adaptivemodulation and coding signaling. The invention is also providing themobile terminal and the base station apparatus for performing themethods described herein.

TECHNICAL BACKGROUND

Third generation (3G) mobile radio systems, such as, for instance,universal mobile telecommunication systems (UMTS) standardized withinthe third generation partnership project (3GPP) have been based onwideband code division multiple access (WCDMA) radio access technology.Today, 3G systems are being deployed on a broad scale all around theworld. After enhancing this technology by introducing high-speeddownlink packet access (HSDPA) and an enhanced uplink, also referred toas high-speed uplink packet access (HSUPA), the next major step inevolution of the UMTS standard has brought the combination of orthogonalfrequency division multiplexing (OFDM) for the downlink and singlecarrier frequency division multiplexing access (SC-FDMA) for the uplink.This system has been named long term evolution (LTE) since it has beenintended to cope with future technology evolutions.

The LTE system represents efficient packet based radio access and radioaccess networks that provide full IP-based functionalities with lowlatency and low cost. The downlink will support data modulation schemesQPSK, 16-QAM, and 64-QAM and the uplink will support QPSK, 16QAM, and atleast for some devices also 64-QAM, for physical data channeltransmissions. The term “downlink” denotes direction from the network tothe terminal. The term “uplink” denotes direction from the terminal tothe network.

LTE's network access is to be extremely flexible, using a number ofdefined channel bandwidths between 1.4 and 20 MHz, compared with UMTSterrestrial radio access (UTRA) fixed 5 MHz channels. Spectralefficiency is increased by up to four-fold compared with UTRA, andimprovements in architecture and signaling reduce round-trip latency.Multiple Input/Multiple Output (MIMO) antenna technology should enable10 times as many users per cell as 3GPP's original WCDMA radio accesstechnology. To suit as many frequency band allocation arrangements aspossible, both paired (frequency division duplex FDD) and unpaired (timedivision duplex TDD) band operation is supported. LTE can co-exist withearlier 3GPP radio technologies, even in adjacent channels, and callscan be handed over to and from all 3GPP's previous radio accesstechnologies.

The overall architecture of an LTE network is shown in FIG. 1 and a moredetailed representation of the E-UTRAN architecture is given in FIG. 2.

As can be seen in FIG. 1, the LTE architecture supports interconnectionof different radio access networks (RAN) such as UTRAN or GERAN (GSMEDGE Radio Access Network), which are connected to the EPC via theServing GPRS Support Node (SGSN). In a 3GPP mobile network, the mobileterminal 110 (called User Equipment, UE, or device) is attached to theaccess network via the Node B (NB) in the UTRAN and via the evolved NodeB (eNB) in the E-UTRAN access. The NB and eNB 120 entities are known asbase station in other mobile networks. There are two data packetgateways located in the EPS for supporting the UE mobility—ServingGateway (SGW) 130 and Packet Data Network Gateway 160 (PDN-GW or shortlyPGW). Assuming the E-UTRAN access, the eNB entity 120 may be connectedthrough wired lines to one or more SGWs via the S1-U interface (“U”stays for “user plane”) and to the Mobility Management Entity 140 (MME)via the S1-MMME interface. The SGSN 150 and MME 140 are also referred toas serving core network (CN) nodes.

As anticipated above and as depicted in FIG. 2, the E-UTRAN consists ofeNodeB 120, providing the E-UTRA user plane (PDCP/RLC/MAC/PHY) andcontrol plane (RRC) protocol terminations towards the user equipment(UE). The eNodeB 120 hosts the Physical (PHY), Medium Access Control(MAC), Radio Link Control (RLC), and Packet Data Control Protocol (PDCP)layers that include the functionality of user-plane header-compressionand encryption. It also offers Radio Resource Control (RRC)functionality corresponding to the control plane. It performs manyfunctions including radio resource management, admission control,scheduling, enforcement of negotiated uplink Quality of Service (QoS),cell information broadcast, ciphering/deciphering of user and controlplane data, and compression/decompression of downlink/uplink user planepacket headers. The eNodeBs are interconnected with each other by meansof the X2 interface.

The eNodeBs 120 are also connected by means of the S1 interface to theEPC (Evolved Packet Core), more specifically to the MME (MobilityManagement Entity) by means of the S1-MME and to the Serving Gateway(SGW) by means of the S1-U. The S1 interface supports a many-to-manyrelation between MMEs/Serving Gateways and eNodeBs 120. The SGW routesand forwards user data packets, while also acting as the mobility anchorfor the user plane during inter-eNodeB handovers and as the anchor formobility between LTE and other 3GPP technologies (terminating S4interface and relaying the traffic between 2G/3G systems and PDN GW).For idle state user equipments, the SGW terminates the downlink datapath and triggers paging when downlink data arrives for the userequipment. It manages and stores user equipment contexts, e.g.parameters of the IP bearer service, network internal routinginformation. It also performs replication of the user traffic in case oflawful interception.

The MME 140 is the key control-node for the LTE access-network. It isresponsible for idle mode user equipment tracking and paging procedureincluding retransmissions. It is involved in the beareractivation/deactivation process and is also responsible for choosing theSGW for a user equipment at the initial attach and at time of intra-LTEhandover involving Core Network (CN) node relocation. It is responsiblefor authenticating the user (by interacting with the HSS). TheNon-Access Stratum (NAS) signaling terminates at the MME and it is alsoresponsible for generation and allocation of temporary identities touser equipments. It checks the authorization of the user equipment tocamp on the service provider's Public Land Mobile Network (PLMN) andenforces user equipment roaming restrictions. The MME is the terminationpoint in the network for ciphering/integrity protection for NASsignaling and handles the security key management. Lawful interceptionof signaling is also supported by the MME. The MME also provides thecontrol plane function for mobility between LTE and 2G/3G accessnetworks with the S3 interface terminating at the MME from the SGSN. TheMME also terminates the S6a interface towards the home HSS for roaminguser equipments.

FIGS. 3 and 4 illustrate the structure of a component carrier in the LTErelease 8. The downlink component carrier of a 3GPP LTE Release 8 issubdivided in the time-frequency domain in so-called subframes, each ofwhich is divided into two downlink slots as shown in FIG. 3. A downlinkslot corresponding to a time period T_(slot) is shown in detail in FIGS.3 and 4 with the reference numeral 320. The first downlink slot of asubframe comprises a control channel region (PDCCH region) within thefirst OFDM symbol(s). Each subframe consists of a give number of OFDMsymbols in the time domain (12 or 14 OFDM symbols in 3GPP LTE (Release8)), wherein each OFDM symbol spans over the entire bandwidth of thecomponent carrier.

In particular, the smallest unit of resources that can be assigned by ascheduler is a resource block also called physical resource block (PRB).With reference to FIG. 4, a PRB 330 is defined as N_(symb) ^(DL)consecutive OFDM symbols in the time domain and N_(sc) ^(RB) consecutivesub-carriers in the frequency domain. In practice, the downlinkresources are assigned in resource block pairs. A resource block pairconsists of two resource blocks. It spans N_(sc) ^(RB) consecutivesub-carriers in the frequency domain and the entire 2·N_(symb) ^(DL)modulation symbols of the subframe in the time domain. N_(symb) ^(DL)may be either 6 or 7 resulting in either 12 or 14 OFDM symbols in total.Consequently, a physical resource block 330 consists of N_(symb)^(DL)×N_(sc) ^(RB) resource elements corresponding to one slot in thetime domain and 180 kHz in the frequency domain (further details on thedownlink resource grid can be found, for example, in 3GPP TS 36.211,“Evolved universal terrestrial radio access (E-UTRA); physical channelsand modulations (Release 10)”, version 10.4.0, 2012, Section 6.2, freelyavailable at www.3gpp.org, which is incorporated herein by reference).While it can happen that some resource elements within a resource blockor resource block pair are not used even though it has been scheduled,for simplicity of the used terminology still the whole resource block orresource block pair is assigned. Examples for resource elements that areactually not assigned by a scheduler include reference signals,broadcast signals, synchronization signals, and resource elements usedfor various control signal or channel transmissions.

The number of physical resource blocks N_(RB) ^(DL) in downlink dependson the downlink transmission bandwidth configured in the cell and is atpresent defined in LTE as being from the interval of 6 to 110 (P)RBs. Itis common practice in LTE to denote the bandwidth either in units of Hz(e.g. 10 MHz) or in units of resource blocks, e.g. for the downlink casethe cell bandwidth can equivalently expressed as e.g. 10 MHz or N_(RB)^(DL)=50RB.

A channel resource may be defined as a “resource block” as exemplaryillustrated in FIG. 3 where a multi-carrier communication system, e.g.employing OFDM as for example discussed in the LTE work item of 3GPP, isassumed. More generally, it may be assumed that a resource blockdesignates the smallest resource unit on an air interface of a mobilecommunication that can be assigned by a scheduler. The dimensions of aresource block may be any combination of time (e.g. time slot, subframe,frame, etc. for time division multiplex (TDM)), frequency (e.g. subband,carrier frequency, etc. for frequency division multiplex (FDM)), code(e.g. spreading code for code division multiplex (CDM)), antenna (e.g.Multiple Input Multiple Output (MIMO)), etc. depending on the accessscheme used in the mobile communication system.

The data are mapped onto physical resource blocks by means of pairs ofvirtual resource blocks. A pair of virtual resource blocks is mappedonto a pair of physical resource blocks. The following two types ofvirtual resource blocks are defined according to their mapping on thephysical resource blocks in LTE downlink: Localised Virtual ResourceBlock (LVRB) and Distributed Virtual Resource Block (DVRB). In thelocalised transmission mode using the localised VRBs, the eNB has fullcontrol which and how many resource blocks are used, and should use thiscontrol usually to pick resource blocks that result in a large spectralefficiency. In most mobile communication systems, this results inadjacent physical resource blocks or multiple clusters of adjacentphysical resource blocks for the transmission to a single userequipment, because the radio channel is coherent in the frequencydomain, implying that if one physical resource block offers a largespectral efficiency, then it is very likely that an adjacent physicalresource block offers a similarly large spectral efficiency. In thedistributed transmission mode using the distributed VRBs, the physicalresource blocks carrying data for the same UE are distributed across thefrequency band in order to hit at least some physical resource blocksthat offer a sufficiently large spectral efficiency, thereby obtainingfrequency diversity.

In 3GPP LTE Release 8 the downlink control signalling is basicallycarried by the following three physical channels:

-   -   Physical control format indicator channel (PCFICH) for        indicating the number of OFDM symbols used for control        signalling in a subframe (i.e. the size of the control channel        region);    -   Physical hybrid ARQ indicator channel (PHICH) for carrying the        downlink ACK/NACK associated with uplink data transmission; and    -   Physical downlink control channel (PDCCH) for carrying downlink        scheduling assignments and uplink scheduling assignments.

The PCFICH is sent from a known position within the control signallingregion of a downlink subframe using a known pre-defined modulation andcoding scheme. The user equipment decodes the PCFICH in order to obtaininformation about a size of the control signalling region in a subframe,for instance, the number of OFDM symbols. If the user equipment (UE) isunable to decode the PCFICH or if it obtains an erroneous PCFICH value,it will not be able to correctly decode the L1/L2 control signalling(PDCCH) comprised in the control signalling region, which may result inlosing all resource assignments contained therein.

The PDCCH carries control information, such as, for instance, schedulinggrants for allocating resources for downlink or uplink datatransmission. The PDCCH for the user equipment is transmitted on thefirst of either one, two or three OFDM symbols according to PCFICHwithin a subframe.

Physical downlink shared channel (PDSCH) is used to transport user data.PDSCH is mapped to the remaining OFDM symbols within one subframe afterPDCCH. The PDSCH resources allocated for one UE are in the units ofresource block for each subframe.

Physical uplink shared channel (PUSCH) carries user data. PhysicalUplink Control Channel (PUCCH) carries signalling in the uplinkdirection such as scheduling requests, HARQ positive and negativeacknowledgements in response to data packets on PDSCH, and channel stateinformation (CSI).

The frequency spectrum for IMT-Advanced was decided at the WorldRadio-communication Conference 2007 (WRC-07). Although the overallfrequency spectrum for IMT-Advanced was decided, the actual availablefrequency bandwidth is different according to each region or country.Following the decision on the available frequency spectrum outline,however, standardization of a radio interface started in the 3rdGeneration Partnership Project (3GPP). At the 3GPP TSG RAN #39 meeting,the Study Item description on “Further Advancements for E-UTRA(LTE-Advanced)” was approved. The study item covers technologycomponents to be considered for the evolution of E-UTRA, e.g. to fulfillthe requirements on IMT-Advanced.

The bandwidth that the LTE-Advanced system is able to support is 100MHz, while an LTE system can only support 20 MHz. Nowadays, the lack ofradio spectrum has become a bottleneck of the development of wirelessnetworks, and as a result it is difficult to find a spectrum band whichis wide enough for the LTE-Advanced system. Consequently, it is urgentto find a way to gain a wider radio spectrum band, wherein a possibleanswer is the carrier aggregation functionality. In carrier aggregation,two or more component carriers (component carriers) are aggregated inorder to support wider transmission bandwidths up to 100 MHz. The term“component carrier” refers to a combination of several resource blocks.In future releases of LTE, the term “component carrier” is no longerused; instead, the terminology is changed to “cell”, which refers to acombination of downlink and optionally uplink resources. The linkingbetween the carrier frequency of the downlink resources and the carrierfrequency of the uplink resources is indicated in the system informationtransmitted on the downlink resources. Several cells in the LTE systemare aggregated into one wider channel in the LTE-Advanced system whichis wide enough for 100 MHz even though these cells in LTE are indifferent frequency bands. All component carriers can be configured tobe LTE Rel. 8/9 compatible, at least when the aggregated numbers ofcomponent carriers in the uplink and the downlink are the same. Not allcomponent carriers aggregated by a user equipment may necessarily beRel. 8/9 compatible. Existing mechanism (e.g. barring) may be used toavoid Rel-8/9 user equipments to camp on a component carrier. A userequipment may simultaneously receive or transmit one or multiplecomponent carriers (corresponding to multiple serving cells) dependingon its capabilities. A LTE-A Rel. 10 user equipment with receptionand/or transmission capabilities for carrier aggregation cansimultaneously receive and/or transmit on multiple serving cells,whereas an LTE Rel. 8/9 user equipment can receive and transmit on asingle serving cell only, provided that the structure of the componentcarrier follows the Rel. 8/9 specifications.

The principle of link adaptation is fundamental to the design of a radiointerface which is efficient for packet-switched data traffic. Unlikethe early versions of UMTS (Universal Mobile Telecommunication System),which used fast closed-loop power control to support circuit-switchedservices with a roughly constant data rate, link adaptation in LTEadjusts the transmitted data rate (modulation scheme and channel codingrate) dynamically to match the prevailing radio channel capacity foreach user.

For the downlink data transmissions in LTE, the eNodeB typically selectsthe modulation scheme and code rate (MCS) depending on a prediction ofthe downlink channel conditions. An important input to this selectionprocess is the Channel State Information (CSI) feedback transmitted bythe User Equipment (UE) in the uplink to the eNodeB.

Channel state information is used in a multi-user communication system,such as for example 3GPP LTE to determine the quality of channelresource(s) for one or more users. In general, in response to the CSIfeedback the eNodeB can select between QPSK, 16-QAM and 64-QAM schemesand a wide range of code rates. This CSI information may be used to aidin a multi-user scheduling algorithm to assign channel resources todifferent users, or to adapt link parameters such as modulation scheme,coding rate or transmit power, so as to exploit the assigned channelresources to its fullest potential.

The CSI is reported for every component carrier, and, depending on thereporting mode and bandwidth, for different sets of subbands of thecomponent carrier. A channel resource may be defined as a “resourceblock” as exemplary illustrated in FIG. 4 where a multi-carriercommunication system, e.g. employing OFDM as for example discussed inthe LTE work item of 3GPP, is assumed. More generally, it may be assumedthat a resource block designates the smallest resource unit on an airinterface of a mobile communication that can be assigned by a scheduler.The dimensions of a resource block may be any combination of time (e.g.time slot, subframe, frame, etc. for time division multiplex (TDM)),frequency (e.g. subband, carrier frequency, etc. for frequency divisionmultiplex (FDM)), code (e.g. spreading code for code division multiplex(CDM)), antenna (e.g. Multiple Input Multiple Output (MIMO)), etc.depending on the access scheme used in the mobile communication system.

Assuming that the smallest assignable resource unit is a resource block,in the ideal case channel quality information for each and all resourceblocks and each and all users should be always available. However, dueto constrained capacity of the feedback channel this is most likely notfeasible or even impossible. Therefore, reduction or compressiontechniques are required so as to reduce the channel quality feedbacksignalling overhead, e.g. by transmitting channel quality informationonly for a subset of resource blocks for a given user.

In 3GPP LTE, the smallest unit for which channel quality is reported iscalled a subband, which consists of multiple frequency-adjacent resourceblocks.

Accordingly, the resource grants are transmitted from the eNodeB to theUE in downlink control information (DCI) via PDCCH. The downlink controlinformation may be transmitted in different formats, depending on thesignaling information necessary. In general, the DCI may include:

-   -   a resource block assignment (RBA), and    -   a modulation and coding scheme (MCS).

The DCI may include further information, depending on the signalinginformation necessary, as also described in Section 9.3.2.3 of the book“LTE: The UMTS Long Term Evolution from theory to practice” by S. Sesia,I. Toufik, M. Baker, Apr. 2009, John Wiley & Sons, ISBN978-0-470-69716-0, which is incorporated herein by reference. Forinstance, the DCI may further include HARQ related information such asredundancy version (RV), HARQ process number, or new data indicator(NDI); MIMO related information such as pre-coding; power controlrelated information, etc. Other channel quality elements may be thePrecoding Matrix Indicator (PMI) and the Rank Indicator (RI). Detailsabout the involved reporting and transmission mechanisms are given inthe following specifications to which it is referred for further reading(all documents available at http://www.3gpp.org and incorporated hereinby reference):

-   -   3GPP TS 36.211, “Evolved Universal Terrestrial Radio Access        (E-UTRA); Physical channels and modulation”, version 10.0.0,        particularly sections 6.3.3, 6.3.4,    -   3GPP TS 36.212, “Evolved Universal Terrestrial Radio Access        (E-UTRA); Multiplexing and channel coding”, version 10.0.0,        particularly sections 5.2.2, 5.2.4, 5.3.3,    -   3GPP TS 36.213, “Evolved Universal Terrestrial Radio Access        (E-UTRA); Physical layer procedures”, version 10.0.1,        particularly sections 7.1.7, and 7.2.

The resource block assignment specifies the physical resource blockswhich are to be used for the transmission in uplink or downlink.

The modulation and coding scheme defines the modulation scheme employedfor the transmission such as QPSK, 16-QAM or 64-QAM. The lower the orderof the modulation, the more robust is the transmission. Thus,higher-order modulations, such as 64-QAM, are typically used when thechannel conditions are good. The modulation and coding scheme alsodefines a code rate for a given modulation, i.e. the number ofinformation bits carried in a predefined resource. The code rate ischosen depending on the radio link conditions: a lower code rate can beused in poor channel conditions and a higher code rate can be used inthe case of good channel conditions. “Good” and “bad” here is used interms of the signal to noise and interference ratio (SINR). The fineradaptation of the code rate is achieved by puncturing or repetition ofthe generic rate depending on the error correcting coder type.

FIG. 6 shows an example of an MCS table used in LTE release 11 todetermine the modulation order (Q_(m)) used in the physical downlinkshared channel. The levels between 0 and 9 in downlink usually representemploying of the robust QPSK modulation. In uplink, LTE release 11foresees an MCS table which essentially has the same structure of theMCS table for the downlink channel. In downlink the QPSK modulationscheme is represented by the MCS levels between 0 and 9 (for moredetails refer to 3GPP TS 36.213, “Evolved Universal Terrestrial RadioAccess (E-UTRA); Physical layer procedures”, version 11.1.0, sections 7and 8, respectively and in particular Tables 7.1.7.1-1 for downlink and8.6.1-1 for uplink). The remaining levels specify configurations withhigher-level modulation schemes. The levels in the MCS tablecorresponding to the higher indexes (17 to 28) represent the 64-QAMmodulation scheme. The QPSK and 16-QAM modulation schemes are alsoindicated as low-order modulation schemes when compared to the 64-QAMmodulation scheme. In general, the term “lower-order modulation scheme”is to be understood as any modulation order lower than the highestsupported modulation order.

The first column of the MCS table defines an index which is actuallysignaled, for instance in the DCI, in order to provide a setting formodulation and coding scheme. The second column of the MCS tableprovides the order of the modulation associated with the index,according to which order 2 means QPSK, order 4 means 16-QAM and order 6means 64-QAM. The third column of the table includes transport blocksize index which refers to predefined sizes of transport blocks and thusalso to a coding rate (amount of redundancy added to the data). Thetransport block size (TBS) index in the third column of the MCS tablerefers to a TBS table (cf. for instance, Table 7.1.7.2.1-1 in the 3GPPTS 36.213, cited above), which includes rows with a first columncorresponding to the number of the TBS index and the following columnsspecifying the transport block sizes for the respective numbers ofresource blocks, which are signaled in the DCI and in particular in theresource block allocation (RBA) part thereof.

Transport block is a data unit which includes data to be transmitted andwhich are provided for the transmission by the higher layers, i.e.mapped onto the physical resources in accordance with the controlinformation including scheduling information and/or according to thesettings by the higher layers. Transport blocks are mapped on therespective resource blocks, i.e. in general onto fixed-size time slots(time domain portions).

In the coming years, operators will begin deploying a new networkarchitecture termed Heterogeneous Networks (HetNet). A typical HetNetdeployment as currently discussed within 3GPP consists of macro and picocells. Pico cells are formed by low power eNBs that may beadvantageously placed at traffic hotspots in order to offload trafficfrom macro cells. Macro and pico eNBs implement the schedulingindependently from each other. The mix of high power macro cells and lowpower pico cells can provide additional capacity and improved coverage.

Generally a terminal, such as a user equipment (UE), connects to thenode with the strongest downlink signal. In FIG. 5A, the areasurrounding the low power eNBs and delimited by a solid line edge is thearea where the downlink signal of the low power eNB is the strongest.User equipments within this area will connect to the appropriate lowpower eNB.

In order to expand the uptake area of a low power eNB without increasingits transmission power an offset is added to the received downlinksignal strength in the cell-selection mechanism. In this manner the lowpower eNB can cover a larger uptake area or in other words the PicoCells are provided with cell rage expansion (CRE). CRE is a means toincrease the throughput performance in such deployments. A UE connectsto a macro eNB only if the received power is at least G dB larger thanthe received power from the strongest pico eNB, where G is thesemi-statically configured CRE bias. Typical values are expected torange from 0 to 20 dB.

FIG. 5A illustrates such a HetNet scenario where various pico cells areprovided in the area of one macro cell. The range expansion zone (CRE)is delimited in FIG. 5A by a dashed edge. The pico cell edge without CREis delimited by a solid line edge. Various UEs are shown located in thevarious cells. FIG. 5B schematically illustrates the concept of a HetNetscenario including a macro eNB and a plurality of pico eNB servingrespectively a plurality of UEs located in their coverage areas.

A heterogeneous deployment with a range expansion in the range of 3 to 4dB has been already considered in the LTE release 8. Nevertheless, theapplicability of CRE with cell selection offsets of up to 9 dB havecurrently being considered at RAN1. However, the additional capacityprovided by the smaller cells may be lost due to signal interferenceexperienced by the UEs in the pico cells. The macro eNB is the singledominant interferer for pico UEs, i.e. for UEs being connected to thepico eNB. This is especially true for pico UEs at the cell edge whenusing CRE.

Cell-edge users served by a pico eNodeB usually have relatively lowreceived signal strength, especially if they are located at the borderof a pico cell with CRE and suffer from strong intercell interference.The major interferer is the eNodeB serving the macro cell in theHeterogeneous Network, which usually transmits subframes at a hightransmission power.

In order to improve the throughput performance of cell-edge mobileterminals, the interference impact has to be reduced on the resource onwhich these mobile terminals are scheduled for downlink transmission.The objective of Inter-Cell Interference Coordination (ICIC) is tomaximize the multi-cell throughput subject to power constraints,inter-cell signaling limitations, fairness objectives and minimum bitrate requirements.

FIG. 7 shows an exemplary downlink transmission scenario in which twoUEs are served by an eNB. Depending on the SINR level on transmissionresources, high or low order modulation schemes can be used for datatransmissions. The set of currently supported modulation schemes in LTEconsists of QPSK, 16-QAM and 64-QAM.

The modulation and coding scheme (MCS) that is used for transmissions ofphysical downlink shared channels (PDSCH) transmissions is indicated bythe MCS field within the downlink control information (DCI). The currentRel-11 MCS field has a fixed length of five bits. This results in 32code points that are used for indicating 32 combinations of modulationscheme and code rate of the channel coder. The code rate is determinedby the transport block size that is mapped onto a set of allocatedresource blocks (RBs).

The interpretation of the MCS field code points is given by thespecified MCS table. The table maps each code points described as MCSindex to a combination of modulation order and transport block size(TBS) index. The modulation order describes the number of bits that aremapped onto a single modulation symbol. The current Release-11 tablesupports modulation order 2, 4 and 6 which corresponds to QPSK, 16-QAMand 64-QAM. The TBS index is linked to an entry of the TBS table whichcontains a transport block size depending in the number of allocatedRBs. Each TBS index corresponds therefore a certain spectral efficiencyin terms of bits transmitted per RB.

The current Release-11 MCS table is shown in FIG. 6. It can be seen thatthe table contains three entries without TBS index. These MCS indicesare used for retransmissions of erroneous transport blocks. Theindication of the transport block size is not required in this casesince the size is known from the initial transmission. Each MCS indexcorresponds to a certain SINR level at which the combination ofmodulation scheme and code rate that is determined by the transportblock size can be used without exceeding a certain block errorprobability. Assuming a block error probability of 0.1, the currentRelease-11 table approximately covers the SINR range between −7 dB and20 dB; the MCS table supports 27 TBS indices, and increasing the TBSindex by one corresponds approximately to an SINR level difference of 1dB.

FIG. 8 shows the RB SINR level distributions of two typical UE within aheterogeneous network deployment as evaluated during performance studiesfor Release-11. The results have been achieved by means of system leveldistributions and the curves correspond to a cell-center UE with veryhigh average SINR level and a cell-edge UE with very low average SINRlevel. From FIG. 8 it can be seen that a large fraction of SINR samplesof the cell-center UE is not covered by the current Rel-11 MCS table.

SUMMARY OF THE INVENTION

In view of the above mentioned problems with the prior art, the aim ofthe present invention is to provide an efficient and robust approach forcovering, with the modulation and coding schemes of the adaptivemodulation and coding, higher SINR conditions.

This is achieved by the features of the independent claims. Advantageousembodiments of the present invention are subject matter of the dependentclaims.

It is the particular approach of the present invention to providemodulation and coding schemes subdivided into two sets, one of whichcovers the lower spectral efficiencies and is advantageously applicablefor lower SINR levels and the other covering the higher spectralefficiencies which is advantageously applicable to higher SINR levels.These sets have the same length in order to be addressable by the samemodulation and coding scheme indicator.

The sets differ by the entries of the highest-order modulation. Thetransmitter and the receiver are able to select between the two (ormore) sets.

According to an aspect of the present invention, an apparatus isprovided for receiving data from a network node in a communicationssystem, the apparatus comprising a control information reception unitfor receiving scheduling information specifying resources on which dataare to be transmitted and including a modulation and coding indicator; amodulation and coding selection unit capable of selecting modulation andcoding from a set of predefined modulation and coding schemes accordingto the modulation and coding indicator, a set selection unit forselecting the set of predefined modulation and coding schemes from atleast two predefined sets—the first set and the second set, which have aplurality of modulation and coding schemes in common and differ in thatthe second set further includes an additional modulation with an orderhigher than any modulation in the first set, and the first set and thesecond set have the same size; and a data transmission unit fortransmitting the data on the scheduled resources using the selectedmodulation and coding.

According to another aspect of the present invention, an apparatus isprovided for transmitting data in a communications system, the apparatuscomprising: a control information transmission unit for transmittingscheduling information specifying resources on which the data are to betransmitted and including a modulation and coding indicator; amodulation and coding selection unit capable of selecting modulation andcoding from a set of predefined modulation and coding schemes accordingto the modulation and coding indicator, a set selection unit forselecting the set of predefined modulation and coding schemes from atleast two predefined sets—the first set and the second set, which have aplurality of modulation and coding schemes in common and differ in thatthe second set further includes an additional modulation with an orderhigher than any modulation in the first set, and the first set and thesecond set have the same size; and a data reception unit for receivingthe data on the scheduled resources using the selected modulation andcoding.

Advantageously, the modulation and coding schemes in each of the setsare associated with the values of modulation and coding indicator, aplurality of the modulation and coding indicator values refer to therespective same modulation and coding schemes in the first and in thesecond set, and the remaining modulation and coding indicator valuesrefer in the second set to the highest-order modulation and in the firstset to modulation(s) of one or more lowest order(s).

According to an embodiment of the present invention, M lowest values ofthe modulation and coding indicator, M being an integer, refer to: themodulation and coding schemes with the lowest-order modulation in thefirst set and the modulation and coding schemes with the highest-ordermodulation in the second set.

The second set may be constructed in such a way that it does not includemodulation with the lowest order included in the first set.

According to an embodiment of the present invention, K values of themodulation and coding indicator, K being an integer, refer to the samemodulation and coding schemes with the lowest-order modulation in boththe first and the second set, L values refer to the modulation andcoding schemes with the lowest-order modulation in the first set and themodulation and coding schemes with the highest-order modulation in thesecond set, and the remaining values of the modulation and codingindicator refer to the same modulation and coding schemes lower than thehighest-order modulation.

Advantageously, the K values correspond to the first K values of theindex and the L values are L values immediately following the K values.

According to an embodiment of the present invention, the modulation andcoding indicator is associated with a modulation and coding schemeincluding a modulation order and a size indicator indicating at leastone of (i) the number of bits in a transport block which is to be mappedonto physical resources and (ii) retransmission without specificindication of the transport block size.

According to an aspect of the present invention, a method is providedfor receiving data from a network node in a communications system, themethod comprising the steps of: receiving scheduling informationspecifying resources on which data are to be transmitted and including amodulation and coding indicator; selecting modulation and coding from aset of predefined modulation and coding schemes according to themodulation and coding indicator, selecting the set of predefinedmodulation and coding schemes from at least two predefined sets—thefirst set and the second set, which have a plurality of modulation andcoding schemes in common and differ in that the second set furtherincludes an additional modulation with an order higher than anymodulation in the first set, and the first set and the second set havethe same size; and transmitting the data on the scheduled resourcesusing the selected modulation and coding.

According to another aspect of the present invention, a method fortransmitting data in a communications system is provided, the methodcomprising: transmitting scheduling information specifying resources onwhich the data are to be transmitted and including a modulation andcoding indicator; selecting modulation and coding from a set ofpredefined modulation and coding schemes according to the modulation andcoding indicator, selecting the set of predefined modulation and codingschemes from at least two predefined sets—the first set and the secondset, which have a plurality of modulation and coding schemes in commonand differ in that the second set further includes an additionalmodulation with an order higher than any modulation in the first set,and the first set and the second set have the same size; and receivingthe data on the scheduled resources using the selected modulation andcoding.

Advantageously, the selection of the set of modulation and codingschemes is performed based on a set selection indicator exchangedbetween the transmitter and the receiver. In particular, the transmitterof data may perform scheduling for the transmission and/or receptionresources and indicate the settings to the receiver of data. Inaddition, the transmitter may indicate to the receiver also the choiceof the set of modulation and coding schemes.

In particular, the set selection indicator may be signaled by means of ahigher-layer signaling. For instance, the scheduling information issignaled on physical layer and the set selection indicator is signaledon the MAC (medium access control) or RRC (radio resource control)layer.

Alternatively, the set selection indicator may be signaled on the samelayer as the scheduling information, for example on the physical layer.For instance, it may be signaled within the control information whichincludes the scheduling information. Some fields used for other purposesmay be used to signal the set selection indicator. For instance, theredundancy version field used for signaling the version of theredundancy for the hybrid ARQ protocol or new data indicator used fordistinguishing between first transmission and retransmission may beused. In particular, some of the values (or a single value) of the RV orNDI may be used to indicate that a first set is to be used and somevalues (or a single value) of the RV or NDI may be used to indicate thata second set shall be used.

Alternatively, the selection of the set of modulation and coding schemesis performed by both receiver and transmitter of the data based on thechannel conditions of their communication channel. For instance, thetransmitter of data receives indication of the channel conditions fromthe receiver of the data and selects the set accordingly. The receiveralso selects the set according to the channel conditions reported to thetransmitter. This approach is implicit and does not require anyadditional signaling. The transmitter and receiver use the same rules toselect the set in dependency of the channel conditions reported.

Preferably, the set selection indicator is signaled(transmitted/received) less frequently than the scheduling information.

It is noted that there may be also other differing entries in thedifferent sets than the entries belonging to the new modulation.

According to an aspect of the present invention a computer-readablemedium is provided with a computer-readable program thereon, which, whenexecuted on the computer, implements the steps of the method accordingto the present invention.

According to an advantageous embodiment, the present invention isapplied to LTE system (for instance Release-11 of the LTE). Inparticular, the data transmitter may be the eNodeB and the data receivermay be the terminal. The data are transmitted over PDSCH and the controlinformation including the scheduling information is transmitted on thePDCCH. The scheduling information may be carried by the DCI. The DCI mayinclude, as is the case in the Release-11 LTE, an MCS index specifyingthe modulation and coding scheme to be used from among a set ofmodulation and coding schemes, which are predefined in a so-called MCStable. In compliance with the invention, more than one MCS tables may bedefined, from which one is used at a time. The MCS table is selectedbased on the signaled information at the terminal or based on thechannel conditions. The MCS table is chosen by the eNodeB based onchannel conditions and the choice may be or does not need to be signaledto the terminal.

The above and other objects and features of the present invention willbecome more apparent from the following description and preferredembodiments given in conjunction with the accompanying drawings inwhich:

FIG. 1 is a schematic drawing showing the general structure of asubframe on a downlink component carrier defined for 3GPP LTE;

FIG. 2 shows an exemplary overview of the overall E-UTRAN architectureof 3GPP LTE;

FIG. 3 shows an exemplary subframe boundary of a downlink componentcarrier as defined for 3GPP LTE;

FIG. 4 is a schematic drawing illustrating an example of a resource gridin a downlink slot in 3GPP LTE;

FIGS. 5A and 5B show a heterogeneous network (HetNet) with one macrocell and various picocells;

FIG. 6 is a table illustrating an example of a modulation and codingscheme table (MCS Table) in a downlink as defined for 3GPP LTE;

FIG. 7 is a schematic drawing illustrating communication of twoterminals with different channel conditions in a cell;

FIG. 8 is a graph exemplifying a distribution of SINR for two terminalswith different channel conditions;

FIG. 9 is a graph exemplifying a distribution of SINR for a set ofmodulation and coding indicator extended by one bit;

FIGS. 10A and 10B are examples of MCS tables in accordance with anembodiment of the present invention;

FIG. 11 is a schematic drawing illustrating the spectral efficiency forthe indices of different MCS tables;

FIG. 12 is a graph exemplifying a distribution of SINR for the MCS tableaccording to an embodiment of the present invention;

FIGS. 13A and 13B are examples of MCS tables in accordance with anembodiment of the present invention;

FIG. 14 is a schematic drawing illustrating the spectral efficiency forthe indices of different MCS tables;

FIG. 15 is a graph exemplifying a distribution of SINR for the MCS tableaccording to an embodiment of the present invention;

FIGS. 16A and 16B are examples of MCS tables in accordance with anembodiment of the present invention;

FIG. 17 is a flow diagram illustrating selection of the MCS table at thetransmitter and/or receiver;

FIG. 18 is a block diagram illustrating the terminals and a network nodeand their structure; and

FIG. 19 is a flow diagram illustrating a method for selecting andapplying the selected modulation and coding scheme.

DETAILED DESCRIPTION

The following paragraphs will describe various embodiments of theinvention. For exemplary purposes only, the embodiments are outlined inrelation to radio access schemes according to 3GPP LTE (Release 8/9) andLTE-A (Release 10/11) mobile communication systems, which were partlydiscussed in the technical background section above. It should be notedthat the invention may be used, for example, in a mobile communicationsystem such as 3GPP LTE-A (release 11) communication systems asdescribed in the technical background section above, but the inventionis not limited to its use in these particular exemplary communicationnetworks. The invention may be, for example, used in non-3GPP systemssuch as WIMAX.

The present invention can be advantageously applied as a strategy forindicating the modulation and coding scheme (MCS) for data transmissionsin an LTE system. The currently supported set of modulation schemes inRelease 11 consists of QPSK, 16-QAM and 64-QAM. However, especially forthe scenarios, in which the terminal is likely to experience ratherstable and good channel conditions in terms of high SINR levels, highermodulation orders may be desirable for achieving higher spectralefficiencies. In particular, 256-QAM may be applied to further extendthe range of spectral efficiencies configurable. First performanceevaluations have shown that the use of 256-QAM is expected to bereasonable with SINR levels of at least 20 dB. The MCS that is used forPDSCH and PUSCH transmissions has up to now been indicated in an MCSfield within the downlink control information (DCI). In view of thisexisting mechanism, it is desirable to ensure that the current signalingscheme can be reused due to backward compatibility. Moreover, therobustness of the signaling with respect to the transmission errorsshould also be maintained as far as possible. In accordance with someadvantageous embodiments of the present invention, concepts for mappingcode points of the Release-11 MCS field to modulation and coding schemescomprising 256-QAM is provided by reinterpreting code points of loworder modulation schemes.

One possibility of extending the achievable spectrum efficiencies is toextend the MCS table by a certain set of entries for 256-QAM withdifferent TBS indices. The MCS field within the DCI has to be extendedaccordingly, in order to cover the resulting increased set of modulationand coding schemes. The minimum MCS field extension consists of a singleadditional bit which doubles the number of MCS field code points. Sincethe current Release-11 MCS field has a length of five bits, the numberof code points would be extended from 32 to 64. The set of modulationand coding schemes could therefore be extended by 32 new entries for256-QAM.

The current Release-11 TBS table does not support transport block sizelarge enough for efficiently making use of 256-QAM which supports veryhigh spectral efficiencies obtained by mapping eight bits onto a single256-QAM modulation symbol. Thus, also the TBS table shouldadvantageously be extended by further rows for transport blocks largerthan the blocks currently supported. This corresponds to the support ofhigher SINR levels.

Assuming that the number of MCS indices is doubled and that theequidistant SINR quantization by approximately 1-dB steps is kept, theabove approach results in extending the SINR range from 27 dB currentlycovered in Release-11 to 54 dB. The effect is shown in FIG. 9 for acell-center UE with high average SINR level. All SINR samples of the UEare covered by the new MCS table. However, a huge fraction of theextended MCS table covers very high SINR levels that will most likelynot be used.

Moreover, the DCI carrying the MCS indicator is mapped onto a set offixed-size resources. Accordingly, the size of the DCI determines therobustness of the signalling carried thereby since it determines howmuch redundancy is to be used for the transmission of the DCI and thus,also of the MCS indicator included therein. The smaller the DCI that ismapped onto a certain resource, the larger is the redundancy and hencethe robustness. Thus, the DCI size should in general be kept as small aspossible.

Another problem of the above described approach of extending the MCSindex by a further bit is that the number of 32 new MCS indices is muchlarger than the set of code rates currently supported, and hence also ofthe transport block sizes which can be supported by the 256-QAM.Extending the modulation order would also further require a set ofadditional code points in the TBS index.

The problem underlying the present invention is based on the observationthat it is not likely for a UE to experience an SINR fluctuation of morethan 50 dB, if the position and hence pathloss and shadowing conditionsdo not change significantly, which is expected to be the case also forthe indoor applications. Therefore, the aim is to primarily cover theexpected SINR level distribution of different UEs by a proper MCS tabledesign.

Even when the above solution and problem have been described for LTE, itis noted that any communications system employing adaptive modulationand coding scheme may beneficially employ the present invention. Inorder to support the adaptive modulation and coding, an apparatus whichis to be able to receive the data (for instance a terminal) from anotherapparatus (such as a network node) in the communications system mayinclude a control information reception unit for receiving schedulinginformation specifying resources on which data are to be transmitted andincluding a modulation and coding scheme indicator and a datatransmission unit for transmitting the data on the scheduled resourcesusing the modulation and coding scheme indicated by the modulation andcoding scheme indicator. It is noted that in general the data receivingapparatus is not necessarily a terminal. It may be also a relay or abase station (for instance in uplink) or any other network node.

Moreover, in order to avoid extension of the modulation and codingindicator by further bit(s), an apparatus for receiving data in thecommunications system in accordance with the present invention comprisesalso a modulation and coding selection unit capable of selectingmodulation and coding from a set of predefined modulation and codingschemes according to the modulation and coding indicator; and a setselection unit for selecting the set of predefined modulation and codingschemes from at least two predefined sets—the first set and the secondset, which have a plurality of modulation and coding schemes in commonand differ in that the second set further includes an additionalmodulation scheme with an order higher than any modulation scheme in thefirst set, and the first set and the second set have the same size.

The above apparatus is an apparatus which receives the data and thescheduling information. However, the present invention also relates to acorresponding apparatus for transmitting the data in a communicationssystem and comprising a control information transmission unit fortransmitting to the terminal scheduling information specifying resourceson which the terminal is to transmit data to the network node andincluding a modulation and coding indicator; a modulation and codingselection unit capable of selecting modulation and coding from a set ofpredefined modulation and coding schemes according to the modulation andcoding indicator; a set selection unit for selecting the set ofpredefined modulation and coding schemes from at least two predefinedsets—the first set and the second set, which have a plurality ofmodulation and coding schemes in common and differ in that the secondset further includes an additional modulation scheme with an orderhigher than any modulation scheme in the first set, and the first setand the second set have the same size; and a data reception unit forreceiving the data from the terminal on the scheduled resources usingthe selected modulation and coding.

For the exemplary case of LTE communication over PDSCH as describedabove, the receiving apparatus may be a terminal, while the transmittingapparatus may be an eNodeB or a relay. However, the receiving apparatusmay also be a relay node and the transmitting apparatus may be aneNodeB. In general, the present invention is not limited to a particulardirection uplink/downlink and also not to a particular type of thenetwork nodes.

More particularly, the modulation and coding schemes in each of the sets(the first set and the second set) may be associated with the values ofmodulation and coding indicator, wherein a plurality of the modulationand coding indicator values refer to the respective same modulation andcoding schemes in the first and in the second set, and the remainingmodulation and coding indicator values refer in the second set to thehighest-order modulation and in the first set to the lowest-ordermodulation(s). It is noted that it is not necessarily only onelowest-order modulation. As can be seen in FIG. 10B, the remainingmodulation and coding indicator values may refer in the second set tothe highest-order modulation and in the first set to modulation(s) ofone or more lowest order(s). For example, FIG. 10B shows that themodulation and coding schemes using modulation order 8 (256-QAM) replacenot only the schemes of modulation order 2 (QPSK) but also some schemesof modulation order 4 (16-QAM) from the table of FIG. 6.

It is noted that even when the sets of the modulation and coding schemesare described above by means of tables, the actual implementation of thesets is immaterial to the present invention. The tabular form merelyvisualises the set of the values and is also used in the current LTEspecifications.

The approach of the present invention, when exemplarily applied to theabove described situation in LTE Release-11, enables to reinterpret thecurrent MCS indices in order to support a new modulation scheme, such as256-QAM for PDSCH transmissions without extending the MCS field withinthe DCI by further bits. This is advantageously achieved by replacingsome entries for a low-order modulation by entries for a new, high-ordermodulation. The rationale is that an UE that will be a candidate forPDSCH transmissions with higher-order modulation schemes will probablynot be used at the same time for transmissions with low-order modulationschemes. This would be, for instance, the case for indoor UEs withrestricted mobility which are located close to a base station (eNB). Itis noted that in view of the current LTE system, extension to 256-QAM isof advantage. However, the present invention is not limited thereto. Inparticular, higher-order modulations may be applicable in future.Moreover, the modulation schemes selectable for the transmission aregenerally not limited to quadrature amplitude modulations and mayinclude any other frequency, phase, amplitude modulation or combinationsthereof including the trellis and coset coding modulation.

In case of the LTE-example, the first set may include modulation andcoding schemes including QPSK, 16-QAM and 64-QAM and the second set mayinclude modulation and coding schemes including the same modulationsand, in addition, 256-QAM. It is also be possible to construct a secondset which does not include the modulation of the lowest order at all,such as QPSK in this example.

It is further noted that the present invention is not limited to twoalternative sets of modulation and coding schemes. A plurality of setsmay be employed. Additional alternative MCS tables selectable enablefiner adaption of the SINR range covered by the terminal channelconditions and/or supporting of a generally higher SINR range. This maybe particularly advantageous for communication systems with variouskinds of deployment scenarios resulting in different channel conditionssuch as heterogeneous cellular and/or mobile networks.

FIGS. 10A and 10B show examples of an MCS table in accordance with anembodiment of the present invention. According to this embodiment, the Mlowest values of the modulation and coding scheme indicator, M being aninteger, refer to:

-   -   the modulation and coding schemes with the lowest-order        modulation in the first set, and    -   the modulation and coding schemes with the highest-order        modulation in the second set.

More particularly, as can be seen in FIG. 10B, the second set does notinclude modulation with the lowest order included in the first set.However, this is only an example, and—as is clear from the example ofFIG. 10A—other arrangements may be beneficial, which also includeschemes with the lowest-order modulation. In particular, FIG. 10A showsan arrangement, according to which only some (not all) of the modulationand coding schemes with the lowest-order modulation are replaced withthe highest-order modulation.

In particular, the modulation order of M lowest MCS indices in the tableshown in FIG. 6 is set to 8 (from 2), which corresponds to 256-QAM(instead of QPSK). FIG. 10A shows an example in which M=6 and FIG. 10Bshows an example in which M=18. However, in general, the presentinvention is not limited thereto and any M may be selected. Accordingly,the M first indices of the first table (such as the table of FIG. 6) arereinterpreted in the second table. The remaining indices of both tablesrefer to the same modulation and coding schemes. In the table of FIG. 6,the M first indices correspond to the indices belonging to the lowestmodulation order and, in particular, correspond to the lowest spectralefficiencies.

In this example, the TBS indices for the MCS indices with theoverwritten modulation order (the entries of the table corresponding to256-QAM) are set to values (cf. values higher than 26 in the exemplaryMCS tables), which are linked with transport block sizes that are largerthan the currently supported sizes for modulation orders of up to 6,which corresponds to 64-QAM. The maximum TBS index in Release-11 is 26.The TBS table has to be then extended by entries for TBS indices largerthan 26. The TBS indices of the adapted entries range from 26 to 31 inthe first adapted MCS table (FIG. 10A), and from 26 to 43 in the secondadapted MCS table (FIG. 10B). The lowest TBS index (26) for 256-QAM isthe same as the highest for 64-QAM. That means that a certain spectralefficiency can be achieved by using either 64-QAM with high code rate,or 256-QAM with low code rate. Which one will be used for datatransmissions depends on the channel conditions and the transmitter andreceiver characteristics. The same approach is used in Release-11 forthe transitions between QPSK and 16-QAM, and between 16-QAM and 64-QAM.However this is only an example which means that, in general, this“repetition” does not have to be applied for the present invention.

The TBS table extension is immaterial for the present invention. It canbe assumed here that the TBS table is extended by a sufficient number ofentries in order to support the required set of code rates for themodulation and coding schemes including the new 256-QAM. It is furthernoted that the present invention is not limited to the formats ofsignaling applied in the LTE. The set of modulation and coding schemesmay correspond to the MCS table as defined in LTE, however does notnecessarily need to. Accordingly, the present invention may supportmodulation and coding schemes given by the modulation order (sincemodulation type is fixed) and by the transport block size indexreferring to particular transport block sizes depending on the number ofresource blocks allocated (signaled within the scheduling information).However, in general, the present invention may apply also to modulationand coding schemes with different modulation types and/or orders. The“coding” may be indicated by means of transport block size or by meansof the coding type applied or in any other means. Moreover, themodulation and coding scheme is not limited to include only a modulationand coding and it may include further indications related to the dataformat such as redundancy version (the case for the uplink in LTE) orother parameters.

The relation between the MCS index and the spectral efficiency of theRelease-11 MCS table is shown schematically in FIG. 11 in the top graph.The spectral efficiency that is determined by the TBS is in the currentMCS table (shown in FIG. 6) increased essentially linearly with the MCSindex. The reoccurring of certain spectral efficiencies at switchingpoints between different modulation orders is neglected in therepresentation of FIG. 11 for the sake of clarity.

The graphs on the bottom of FIG. 11 show how the spectral efficienciesare changed for low MCS indices of the MCS tables shown in FIGS. 10A and10B, which now support 256-QAM. Since each spectral efficiency valuecorrespond to a certain SINR level, it can be seen that the SINR rangecovered by each MCS table is shifted from lower to higher SINR levels.The graph on the left side of FIG. 11 illustrates the general case inwhich there are M first values of the first MCS table (Table of FIG. 6)replaced by the entries with highest-order modulation, namely the256-QAM. The graph on the right side of FIG. 11 illustrates the case inwhich M=6 (the index numbering in these examples starts with 0).

Each UE is expected to be operated within a certain SINR range that isdetermined by its position (location with respect to the base station)and multipath channel properties in particular in terms of small-scalefading. The idea underlying the present invention is to reinterpret MCSindices and thus shift the SINR range that is covered by the MCS tablerather than to extend the SINR range. It is expected that the currentSINR range in LTE of approximately 27 dB is sufficient for all UEs. Asis understood by those skilled in the art, an appropriate shift shouldbe applied in order to cover the real SINR levels experienced by the UEsin the cell of the communications system.

The present invention may be advantageously employed in that two or moredifferent MCS tables, which cover different SINR ranges, are defined inthe communication standard such as the LTE specification, and eachterminal is informed about the MCS table to be used for the PDSCHtransmissions. Exemplary ways in which the terminals obtain theinformation regarding the MCS table shall be discussed later.

Since the different MCS tables are to cover different SINR ranges, itcan also be beneficial to allow the support of different MCS tables fordifferent subframe sets or subbands in order to support differentinterference conditions on these sets of radio resources. For instance,different MCS tables may be supported for low power subframes than forthe regular subframes. Accordingly, a terminal may automatically selecta first table for the transmission in the low power subframes and asecond table for the transmission in the remaining subframes. Inparticular, transmission in the low power subframes may employ an MCStable with more lower-order modulations in order to be more robust,while the transmission in the remaining subframes may use another MCStable including a higher-order modulation in accordance with anyembodiment of the present invention. Low-power subframes are employedespecially in the field of radio transmission and, in particular, forthe heterogeneous networks. Accordingly, some subframes are transmittedwith a reduced power, which is generally kept lower than thetransmission power of the remaining (regular) frames. The power may belimited by a threshold. The limited power frames are particularly usefulat the borders of the pico cells at which the pico cell receiver and thelarger cell receiver signals may interfere. They enable a terminal toreceive data from pico cells even when the base station of the macrocell is more powerful (cf. FIGS. 5A and 5B and the related descriptionabove).

Moreover, different component carriers may employ different MCS tables,meaning that the MCS table can be selected by the terminal differentlyfor different component carriers.

FIG. 12 shows exemplarily the RB SINR level distribution of a typicalcell-center UE and the corresponding appropriate MCS table shift thatcovers more or less all SINR samples. As can be seen when compared toFIG. 8, the SINR range width has not been changed but rather the SINRrange has been shifted towards the higher SINRs. Accordingly, in theabove described embodiment, linear shift of the SINR range covered bythe MCS table is performed.

Correspondingly, in the example tables of FIG. 10, the most robust(low-order modulation(s), small transport block size) modulation andcoding schemes have been replaced by the most spectrum-efficient(high-order modulation(s), large transport block sizes) schemes. Thismeans that very robust combinations of modulation and coding scheme arenot available anymore if MCS table entries for 256-QAM are supported.

However, sometimes it may be desirable to support a certain set of veryrobust combinations of modulation and coding even in case of very goodaverage channel conditions, i.e. in case of average to high SINR level.

Thus, according to another embodiment of the present invention, K valuesof the modulation and coding indicator, K being an integer, refer to thesame modulation and coding schemes with the lowest-order modulation inboth the first and the second set, L values, L being an integer, referto the modulation and coding schemes with the lowest-order modulation inthe first set and the modulation and coding schemes with thehighest-order modulation in the second set, and the remaining values ofthe modulation and coding indicator refer to the same modulation andcoding schemes lower than the highest-order modulation.

It is noted that according to an advantageous implementation, the Kvalues are the K lowest values of the modulation and coding indicatorand the L values are the L values following the K values.

An example of possible MCS tables according to such advantageousimplementation is illustrated in FIGS. 13A and 13B. The tables may berespectively advantageous for two different UEs with different averagechannel conditions. In both MCS tables of FIG. 13, the lowest K=2entries are not overwritten in order to support very robust datatransmissions. It is noted that the value K=2 has been chosenexemplarily. Alternatively, there may be also a single one most robustmodulation and coding scheme (K=1) left (for instance also in the firstposition in the MCS table, i.e. having the lowest index value in theset). However, K may also be larger. In FIG. 13A, L=4, whereas in FIG.13B, L=16.

The particular selection of M, K, L in the above embodiments is to beperformed according to the scenarios, in which the devices of thecommunications system taking part on the communication using theadaptive modulation and coding typically operate. As is clear to thoseskilled in the art, in order to determine M, K, L,measurements/estimation of the SINR for the desired deployment scenariosshould be performed and based thereon decided, which SINR range is to becovered by the respective sets of the modulation and coding schemes.

It is noted that these exemplary MCS tables of FIG. 13, as well as thetables of FIG. 10, represent separate tables: the communication systemnodes (terminal, relay and/or base station, eNodeB) may be configured touse the table of FIG. 6 as the first set and the table of FIG. 10A (oralternatively 10B or alternatively 13A or 13B) as the second set. Thismeans that there may be only two sets selectable. This scenario has anadvantage of low signalling overhead when the selection of the set is tobe signalled from the transmitter of data to the receiver of data.Still, having two sets of modulation and coding schemes suffices todistinguish between the devices (terminals, relays) operating in therange of lower to normal SINRs and the devices operating in the range ofhigh SINRs, for instance due to a deployment scenario such as pico-cellin an indoor environment with line of sight to the base station (orrelay) and/or located near to the centre of the cell.

However, the present invention is not limited thereto. There may be morethan two sets of modulation and coding schemes selectable. For instance,there may be a the set of FIG. 6 and two other sets of the respectiveFIGS. 10A and 10B, or sets of the FIGS. 10A and 13B, or any othercombination. It may be beneficial to have more than three sets toselect. This will depend on the amount of distinct scenarios in which adevice is to be capable to operate, in particular with respect to therange of SINRs (and, correspondingly, range of spectral efficiency).

The resulting association between MCS index and spectral efficiency forthe example of FIG. 13 is schematically illustrated by the graphs ofFIG. 14. In particular, on the left side of FIG. 14, the general case ofL and K is shown, which approximately corresponds to the table shown inFIG. 13B, in which K=2 and L=16. On the right side of FIG. 14, the graphcorresponds, with K=2 to the table shown in FIG. 13A (with L=4, when theMCS index starts with 0).

FIG. 15 shows how the SINR samples of a typical cell-center UE (a UEwhich operates in a range of higher SINRs) are covered by the MCS tableshown in FIG. 13A. The MCS indices for the low SINR values can always beused for data transmissions on resource blocks with higher SINR levels.However, the opposite is not possible since for the lower SINRs thechannel quality would be low and consequently, the error rate to high tobe able to decode the data. The MCS indices for very robust datatransmissions, such as the first K indices, are beneficial fortransmissions of very error sensitive messages such as control messagesor user data transmissions with very high quality of service (QoS)requirements in terms of error robustness, which may be in particularthe delay sensitive services in which the retransmissions are notfeasible. This may be for instance real-time conversational (and/orstreaming) applications.

The cost for supporting certain MCS indices for very robust datatransmissions is that less MCS levels for very high spectralefficiencies can be supported. This trade-off has to be taken intoaccount when defining an appropriate MCS table. One single MCS index forvery robust data transmissions with QPSK should be sufficient since theprobability for such high requirements for very robust datatransmissions is expected to be very low in case of high average SINRlevels, as can be seen in FIG. 15.

As illustrated in the above described figures, the modulation and codingscheme indicator may be associated with a particular modulation andcoding scheme including: a modulation order and a size indicatorindicating at least one of (i) the number of bits in a transport blockwhich is to be mapped onto physical resources and (ii) retransmissionwithout specific indication of the transport block size. For instance,in FIGS. 6, 10, and 13, the first 29 entries of the respective tablesassociate the MCS index 0 to 28 with respective combinations of amodulation order and a TBS index. However, the last three indices 29 to31 indicate for three respective modulation orders 2, 4, and 6“reserved” which means that these values are reserved for HARQretransmissions performed with the indicated modulation order. Nospecific size/number of the transport blocks is necessary to be signaledsince the size is determined in a predefined manner from the TBS usedfor the first transmission.

In accordance with an embodiment of the present invention, which iscombinable with any of the above described embodiments, for thehighest-order modulation in the second set of modulation and codingschemes, also an entry is added indicating retransmission withoutspecifying explicitly the transport block size and the number oftransport block as it is done by the TBS index. In particular, thereservation of a certain MCS index for HARQ retransmissions with 256-QAMmay be performed by reserving the first index (the lowest value of themodulation and coding indicator). This has the advantage of maintainingthe equality of higher-order modulation entries in both (or all) sets sothat even when there was a mismatch of set selection between thereceiving and transmitting node, in most cases no error would occur. Inthe same way as done for the other modulation schemes, it is notrequired to specify a certain TBS index for that entry since thetransport block size is known from the initial transmission.

An example, in which MCS index 0 is used for indicating theretransmissions for the highest-order modulation, namely for 256QAM, isshown in FIGS. 16A and 16B. In FIG. 16A, the 5 indices of the MCS indexfollowing the first index (with value 0) are dedicated to modulation andcoding schemes with the highest-order modulation (order 8, correspondingto 256-QAM), followed by the same schemes as those of FIG. 6 for theindex values from 6 to 31. FIG. 16B shows an example, in which the firstMCS index (with value 0) is followed by 17 schemes employing thehighest-order modulation. Again, the remaining schemes are the sameschemes as those of FIG. 6 for the index values from 18 to 31.

It is noted that the reservation of an MCS Index for HARQretransmissions may also be applied together with maintaining someentries of the lowest-order modulation (as described with reference toFIG. 13). Both variants are possible: the retransmission index may bethe first one in the table or it may follow the M lowest-ordermodulation schemes. Combination of providing an HARQ-reserved index withmaintaining some of the most robust modulation and coding schemesprovides a high degree of flexibility. HARQ retransmissions with 256-QAMare possible and at least one MCS index is kept for very robust datatransmissions using QPSK.

In the following, exemplary embodiments are provided concerning theperforming of the selection of the set of modulation and coding schemesfrom the predefined sets. It is noted that any of the followingexemplary embodiments may be combined with any of the previouslydescribed embodiments.

According to an embodiment of the present invention, the choice of theset is performed by the network node, signaled to the terminal, and theselection of the set at the terminal is performed accordingly, whereinthe signaling is a higher-layer signaling less frequent than thesignaling of the modulation and coding scheme indicator.

In terms of LTE terminology, the MCS table is indicated by higher layersignaling. The indication of the set (MCS table) is carried out byeither MAC or RRC messages which are sent in downlink direction (fromthe eNB to the UE, or alternatively from the eNB to the relay or fromthe relay to the UE). This approach yields a semi-static configurationof the used MCS table by means of higher layer information elements. Theterm semi-static implies that in comparison with the dynamic scheduling,allocation and MCS control, the MCS table selection is performed lessfrequently. The frequency may be selected according to therequirements—if the channel conditions change so that a change of theMCS table may be beneficial, then the new table is indicated. The datatransmitting node thus chooses the MCS table, signals the choice bymeans of a set indicator to the data receiving node and the datareceiving node selects then the set (MCS table) according to thereceived set indicator.

This embodiment provides an advantage of simple and robustimplementation. The switching between four MCS tables would require onlytwo additional bits in the higher-level signaling, the switching betweentwo MCS tables (for example the standard Release-11 table as shown inFIG. 6 and the adapted table for 256-QAM) would require only one bit.

However, the present invention is not limited to signaling of the setselection indicator within the higher-layer signaling. Alternatively, inaccordance with another embodiment of the present invention, the choiceof the set is performed by the network node, signaled to the terminal,and the selection of the set at the terminal is performed accordingly,wherein the signaling is carried on the same layer as the signaling ofthe modulation and coding indicator, but less frequently.

In particular, in the context of the LTE, the indication may beadvantageously conveyed by reusing code points of the DCI. This approachyields a dynamic MCS table adaptation that can be changed from subframeto subframe but does not necessarily have to be changed. In general, theset selection indication may be included within the schedulinginformation.

In LTE it can be expected that 256QAM would be mainly used for initialtransmissions of a transport block. The reason is that if a firsttransmission with 256QAM fails, it is likely that the cause for thefailure is imperfect channel estimation or the fading of the channelthat has made the quality inferior. In both of these cases, it isbeneficial to use a more robust modulation scheme for anyretransmissions in order to decrease the probability of sustaineddecoding failures. This behavior could be exploited by tying the 256QAMextension to the MCS table to a first transmission of a transport block.

This may be performed based on the NDI indicator. The NDI indicator isan indicator for distinguishing between the first transmission of dataand data retransmission. Accordingly, it is usually a one-bit flag. Thisis also the case in LTE.

In particular, the following interpretation of the signaling may beenabled or disabled by means of a semi-static configuration, forinstance by a higher layer protocol such as RRC or MAC:

-   -   Upon detection of a toggled NDI, apply the 256-QAM version of        the MCS table to the interpretation of the 5-bit MCS field        whereas    -   Upon detection of a non-toggled NDI, apply the Release-11 MCS        table to the interpretation of the 5-bit MCS field

Here, “toggled” means set to indicate new data, i.e. first transmissionof the data. Correspondingly “non-toggled” means set to indicateretransmission of data.

However, it is noted that the interpretation may also be specified asmandatory and does not have to be controlled by the higher-levelsignaling. The control by the higher layer signaling provides anadvantage of backward compatibility.

Generally formulated, the selection of the set of modulation and codingschemes is performed based on whether the data to be modulated/coded aredata transmitted for the first time (new data) or a retransmission. Thisselection may be performed at the transmitter an the receiver in thesame way, and in particular at the receiver based on the new dataindicator. The above example is based on the observation that for thefirst transmission, the assumption of good channel conditions may bemade and thus, the second set of modulation and coding schemes includingthe highest-order modulation may be used. If the transmission was notsuccessful, so that a retransmission is necessary, this may indicatethat the channel conditions are worse and thus, the first set isselected, which does not include the highest-order modulation.

However, the interpretation does not need to be based (only) on the NDI.Alternatively, or in addition, the redundancy version (RV) may be usedfor this purpose.

In particular, the following interpretation of the signaling could beenabled or disabled by means of a semi-static configuration, forinstance by a higher layer protocol such as RRC or MAC:

-   -   Upon detection of RV=0, apply the 256-QAM version of the MCS        table to the interpretation of the 5-bit MCS field.    -   Upon detection of RV=1/2/3, apply the Release 11 MCS table to        the interpretation of the 5-bit MCS field.

It is to be noted that the above assignment of the values is onlyexemplary. Alternatively, other RV values could be used instead of 0 toindicate the use of 256-QAM. The 5-bit MCS field refers to the MCS tablesize of 32 entries as illustrated in FIG. 6 and to an advantageousembodiment of the present invention, according to which the first set isthe current LTE table shown in FIG. 6 and the second set is a table withthe same number of entries but including instead of some entries withlowest-order modulation new entries with a modulation, the order ofwhich is higher than any modulation on the first set.

It is noted that the interpretation may also be specified as mandatoryand does not have to be controlled by the higher-level signaling. Thecontrol by the higher layer signalling provides an advantage of backwardcompatibility.

Generally speaking, redundancy version indicator (may correspond to afield in a control information) specifies the version of redundancy tobe applied when retransmitting data. Namely, hybrid ARQ schemes performsretransmissions by using different redundancy schemes in order toachieve higher diversity and better probability of correct decoding.Thus, the redundancy version is also an indication for theretransmitting and, in addition, for a number of retransmissionsperformed so far. Accordingly, this information may be also used forswitching between the sets of modulation and coding schemes. Redundancyversion 0 is used with no retransmissions and may thus advantageously beused to indicate selection of the second set of modulation and codingschemes, which includes the highest-order modulation (256-QAM). Theremaining values of the RV may be used to select the first set withoutthe highest-order modulation. Alternatively, the different redundancyversion values may be used to select different sets (i.e. select betweenmore than 2 MCS tables). The higher the number of retransmissions, themore robust set of modulation and coding schemes is selected preferably.

The above examples rely on explicit signaling of a set selectionindicator. Another approach is the implicit MCS table indication.

In accordance with another embodiment of the present invention, theselection of the set is performed by both terminal and network nodebased on the terminal's channel conditions reported from the terminal tothe network node. Accordingly, no exchange of an explicit indication isnecessary in order to select the set of the modulation and codingschemes.

In the context of the LTE, the MCS table may be determined by theaverage channel quality of the UE that is captured by the wideband CQIwhich is reported from the UE to the eNB. This approach does not requireany additional signaling and automatically adapts the MCS table to theprevailing channel conditions. It has to be specified, which widebandCQI values yield an MCS table switching so that the switching (selectingof an MCS table different from the currently employed MCS table) isperformed in the same way at the transmitter and the receiver such aseNodeB and the UE (or other combination of relay, eNodeB and terminal).

An exemplary MCS table selection strategy based on the reported widebandCQI is provided in FIG. 17. Accordingly, two CQI thresholds T1 and T2>T1are defined in order to enable switching between different MCS tables.MCS Table A is used in case of bad channel conditions with low SINRlevels, MCS Table B for medium SINR levels, and MCS Table C for highSINR levels.

The process starts by decision 1710 on whether a channel quality measureemployed exceeds a first threshold, T1. If not, a first set ofmodulation and coding schemes is selected 1720 (MCS table A). If yes, itis further judged 1730 whether the channel quality measure exceeds asecond threshold, T2. If this is not the case, then a second set (MCStable B) of modulation and coding schemes is selected 1740. If yes, athird set of modulation and coding schemes (MCS table C) is selected1750. It is noted that this example is not meant to limit the presentinvention. Alternatively, a selection between two sets may be performedbased on a single threshold. This would correspond to the steps1730-1750 of FIG. 17 and selection between the MCS table B and C.Moreover, the decision may be performed for more than three sets (MCStables) based on the corresponding number of thresholds (for P tables,P−1 thresholds).

In yet another embodiment, the usage of a particular MCS table is linkedto a usage of a certain DCI format, i.e. of the control information,which contains also the (dynamic) scheduling information including themodulation and coding indicator. In terms of the LTE-embodiment, sinceDCI format 1A is used for robust data transmissions in general, it isnot required to support 256-QAM for the corresponding datatransmissions. Therefore, according to this embodiment, the standardRelease-11 MCS table is used in combination with DCI format 1A. For theother DCI formats it can be indicated in semi-static or dynamic mannerwhich MCS table is to be used. The downlink control information formatincluding the DCI formats in LTE can be found, for instance, in thespecification 3GPP TS 36.212 v.11.1.0, Section 5.3.3 “Downlink ControlInformation” and, in particular in the subsection 5.3.3.1 “DCI formats”,incorporated herein by reference.

In general, the scheduling information which includes the modulation andcoding scheme is a part of control information (such as downlink controlinformation). The control information can have different formats.According to this embodiment, each set of modulation and coding schemesis associated with a particular format (or more formats) of the controlinformation unambiguously in such a way that based on the controlinformation format, it can be decided, which set is to be select. Forexample, there is a first control information format associated with afirst set and second control information associated with a second set.However, there may be more control information formats associated witheach the first set and the second set.

Although the above description mainly refers to MSC tables for thedownlink, the same concept can be analogously applied to the MCS tablefor the uplink.

FIG. 18 illustrates examples of devices in accordance with the presentinvention. In particular, FIG. 18 shows two terminals 1810 and 1820. Theterminal 1810 is a terminal capable of transmitting data with amodulation and coding scheme indicated within the schedulinginformation, being a part of control information. Terminals 1810 and1820 may use different sets of modulation and coding schemes since theymay experience different channel conditions. Terminal 1810 works indownlink, terminal 1820 in uplink in this example. A single terminal maybe provided capable of applying bundling in both uplink and downlinkdirection. Such a terminal would then include the functional blocks ofboth terminals 1810 and 1820. FIG. 18 further shows a scheduling node1890. The scheduling node 1890 schedules the transmission and receptionof data by the terminals. The scheduling node may be a network node suchas a base station or a radio network controller or the like and inparticular an eNodeB. For instance, in LTE the eNodeB performs thedynamic scheduling for the shared channels in downlink (PDSCH) and inuplink (PUSCH). However, it is noted that in general, in LTE or othersystems the scheduling may be performed by a different node or for otherdownlink or uplink channels, which is still no problem for theemployment of the present invention in such a system.

In accordance with an embodiment of the present invention, a terminal1820 is provided for transmitting data in a multicarrier communicationsystem in which the transmission of data is performed in transmissiontime intervals. The terminal 1820 includes a control informationreception unit 1825 for receiving scheduling information indicatingresources on which the terminal is scheduled to transmit data, andincluding a set of modulation and coding indicators for indicating themodulation scheme and the size of the data according to which data is tobe transmitted. Moreover, the terminal comprises a data transmissionunit 1827 for transmitting the data in the scheduled resources and inaccordance with the received modulation and coding indicator andaccording to a transmission parameter of the data to be transmitted. Inparticular the transmission parameter may be used for selecting themodulation and coding scheme to be used for coding data to betransmitted.

In accordance with another embodiment of the present invention, aterminal 1810 is provided for receiving data in a multicarriercommunication system, in which the reception of data is performed intransmission time intervals. Such a terminal 1810, similarly to theterminal 1820, for receiving scheduling information indicating resourceson which the terminal is scheduled to transmit data, and including a setof modulation and coding indicators for indicating the modulation schemeand the size of the data according to which data is to be transmitted.Moreover, the terminal comprises a data transmission unit 1827 fortransmitting the data in the scheduled resources and in accordance withthe received modulation and coding indicator and according to atransmission parameter of the data to be transmitted. In particular thetransmission parameter may be used for selecting the modulation andcoding scheme to be used for coding data to be transmitted.

The transmission parameter may be for instance the transmission power atwhich the data are transmitted. Alternatively, the transmissionparameter may be linking information capable of linking a particularsubframe set to a corresponding modulation and coding scheme indicator.

The modulation and coding indicator set, for instance one or more of MCStables, may be included in the scheduling information. The modulationorder field and the TBS index may be a separate field or bit within amodulation and coding indicator. Alternatively, the modulation orderfield and the TBS index may be implemented as a single field.

The modulation and coding indicator may be semi-statically chosen amongthe received modulation and coding indicator set by comparing, at aselection unit 1813 or 1823 the power level at which the data are to bereceived or transmitted. This can be done according to the stepsdescribed with reference to FIG. 17. However this is not to limit thepresent invention. In particular, the selection unit 1813 or 1823 mayselect the modulation and coding scheme set according to a signalled setselection indication and the modulation and coding scheme therefrombased on the modulation and coding indicator. Alternatively, thecomparison may be performed at the reception unit 1815 or 1825. Theselection unit 1813 or 1823 may include the above described modulationand coding selection unit and the set selection unit. In addition oralternatively the reception unit 1815 or 1825 may further be adapted toselect the appropriate modulation and coding indicator according to oneof the methods of the present invention.

Alternatively, the modulation and coding indicator may be signalled tothe terminal 1810 or 1820 by a semi-static configuration, such as a RRCor MAC configuration. In particular, the appropriate MCS table to beused can be directly indicated by the eNB. However, this is not to limitthe present invention. In alternative embodiments the linking indicatordoes not have to be necessarily configured by the RRC. Any other type ofsignalling may be used. The term semi-statically here refers to the factthat the signalled value applies for more than one scheduledtransmission and or reception.

The terminal may be a mobile or a static terminal. However, the terminalmay also be a normal user terminal or a relay node. The multicarriercommunication system may be a wireless communication system supportingorthogonal frequency division modulation (OFDM), such as LTE. However,the present invention is not limited thereto and modulation and codingscheme of the present invention may be applied to any communicationsystem supporting dynamic scheduling on a shared data or controlchannel. The transmission time interval here refers to a predefinedprocessing time interval in which the data are provided to the physicallayer for transmission in a subframe (predefined duration on a radiointerface). For instance, the length of the TTI in LTE is onemillisecond and one TTI is mapped on the physical resources of onesubframe as already described in the background section. It is notedthat these values apply for the current LTE specifications. However, thepresent invention is applicable for any timing of the radio interface.

The present invention further provides methods for transmission andreception of data. One of such methods is illustrated in FIG. 19.

In particular, a method is provided for transmitting and/or receivingdata in a multicarrier communications system, transmission and/orreception of data being performed in transmission time intervals. Themethod is to be performed at a scheduling node and comprisestransmitting 1920 scheduling information, which indicates resources onwhich a terminal is scheduled to transmit or receive data and includingscheduling information indicating resources on which the terminal isscheduled to transmit data, and including a set of modulation and codingindicators for indicating the modulation scheme and possibly the setselection indicator and the size of the data according to which data isto be transmitted. The method further includes transmitting 1280 and/orreceiving 1960 the data in the scheduled resources (over a channel 1901)to/from the terminal in accordance with the transmitted modulation andcoding indicator and on a transmission parameter of the data to betransmitted/received 1910, 1915. It is noted that FIG. 19 shows a stepof configuring 1910, 1915 the terminal transmission or reception of data(corresponding to configuring the scheduling node own reception andtransmission of data respectively). This step may be a part ofscheduling performed by the scheduling node and may include selection ofthe resources and judging which modulation and order indicator has to bechosen among the set of modulation and coding indicators as well as theselection of the set of modulations and coding schemes. Theconfiguration step provides a result (configuration) to the terminal viatransmission. On the other hand, the scheduling node also handlesaccording to this configuration 1960, 1980, i.e. transmits or receivesdata in the configured resources.

Although in the embodiments considered above the MCS tables have beendescribed with reference to subframes. It has to be understood that theconcepts above and the principles of the invention can be also appliedto subbands. In particular, it has to be understood that several MCStables, for instance adapted to take into account varying transmissionpowers, could be designed and associated to different correspondingsubbands.

Moreover, the principles described above can be applied to anycommunication system, such as multicarrier communication systems.

The explanations given in the Technical Background section above areintended to better understand the specific exemplary embodimentsdescribed herein and should not be understood as limiting the inventionto the described specific implementations of processes and functions inthe mobile communication network such as a network compliant with the3GPP standards. Nevertheless, the improvements proposed herein may bereadily applied in the architectures/systems described in theTechnological Background section and may in some embodiments of theinvention also make use of standard and improved procedures of thesesarchitectures/systems. It would be appreciated by a person skilled inthe art that numerous variations and/or modifications may be made to thepresent invention as shown in the specific embodiments without departingfrom the spirit or scope of the invention as broadly described.

Another embodiment of the invention relates to the implementation of theabove described various embodiments using hardware and software. It isrecognized that the various embodiments of the invention may beimplemented or performed using computing devices (processors). Acomputing device or processor may for example be general purposeprocessors, digital signal processors (DSP), application specificintegrated circuits (ASIC), field programmable gate arrays (FPGA) orother programmable logic devices, etc. The various embodiments of theinvention may also be performed or embodied by a combination of thesedevices.

Further, the various embodiments of the invention may also beimplemented by means of software modules, which are executed by aprocessor or directly in hardware. Also a combination of softwaremodules and a hardware implementation may be possible. The softwaremodules may be stored on any kind of computer readable storage media,for example RAM, EPROM, EEPROM, flash memory, registers, hard disks,CD-ROM, DVD, etc.

Summarizing, the present invention relates to adaptive modulation andcoding scheme selection and signaling in a communication system. Inparticular, a modulation and coding scheme to be used for transmissionof a data is selected from a set of predetermined modulation and codingschemes. The predetermination of the set is performed by selecting theset from a plurality of predefined sets. The sets have the same size, sothat a modulation and coding selection indicator signaled to select themodulation and coding scheme may be advantageously applied to any of theselected sets. Moreover, a second set includes schemes with a modulationnot covered by the schemes of a first set, and which is of a higherorder than any modulation in the first set.

1. An apparatus for receiving data from a network node in acommunications system, the apparatus comprising: a control informationreception unit for receiving scheduling information specifying resourceson which data are to be transmitted and including a modulation andcoding indicator; a modulation and coding selection unit capable ofselecting modulation and coding from a set of predefined modulation andcoding schemes according to the modulation and coding indicator, a setselection unit for selecting the set of predefined modulation and codingschemes from at least two predefined sets—the first set and the secondset, which have a plurality of modulation and coding schemes in commonand differ in that the second set further includes an additionalmodulation with an order higher than any modulation in the first set,and the first set and the second set have the same size; and a datatransmission unit for transmitting the data on the scheduled resourcesusing the selected modulation and coding.
 2. An apparatus fortransmitting data in a communications system, the apparatus comprising:a control information transmission unit for transmitting schedulinginformation specifying resources on which the data are to be transmittedand including a modulation and coding indicator; a modulation and codingselection unit capable of selecting modulation and coding from a set ofpredefined modulation and coding schemes according to the modulation andcoding indicator, a set selection unit for selecting the set ofpredefined modulation and coding schemes from at least two predefinedsets—the first set and the second set, which have a plurality ofmodulation and coding schemes in common and differ in that the secondset further includes an additional modulation with an order higher thanany modulation in the first set, and the first set and the second sethave the same size; and a data reception unit for receiving the data onthe scheduled resources using the selected modulation and coding.
 3. Theapparatus according to claim 1, wherein the modulation and codingschemes in each of the sets are associated with the values of modulationand coding indicator, a plurality of the modulation and coding indicatorvalues refer to the respective same modulation and coding schemes in thefirst and in the second set, and the remaining modulation and codingindicator values refer in the second set to the highest-order modulationand in the first set to modulation(s) of one or more lowest order(s). 4.The apparatus according to claim 1, wherein M lowest values of themodulation and coding indicator, M being an integer, refer to: themodulation and coding schemes with the lowest-order modulation in thefirst set, and the modulation and coding schemes with the highest-ordermodulation in the second set.
 5. The apparatus according to claim 1,wherein the second set does not include modulation with the lowest orderincluded in the first set.
 6. The apparatus according to claim 1,wherein: K values of the modulation and coding indicator, K being aninteger, refer to the same modulation and coding schemes with thelowest-order modulation in both the first and the second set, L valuesrefer to the modulation and coding schemes with the lowest-ordermodulation in the first set and the modulation and coding schemes withthe highest-order modulation in the second set, and the remaining valuesof the modulation and coding indicator refer to the same modulation andcoding schemes lower than the highest-order modulation.
 7. The apparatusaccording to claim 1, wherein the modulation and coding indicator isassociated with a modulation and coding scheme including: a modulationorder and a size indicator indicating at least one of (i) the number ofbits in a transport block which is to be mapped onto physical resourcesand (ii) retransmission without specific indication of the transportblock size.
 8. A method for receiving data from a network node in acommunications system, the method comprising the steps of: receivingscheduling information specifying resources on which data are to betransmitted and including a modulation and coding indicator; selectingmodulation and coding from a set of predefined modulation and codingschemes according to the modulation and coding indicator, selecting theset of predefined modulation and coding schemes from at least twopredefined sets—the first set and the second set, which have a pluralityof modulation and coding schemes in common and differ in that the secondset further includes an additional modulation with an order higher thanany modulation in the first set, and the first set and the second sethave the same size; and transmitting the data on the scheduled resourcesusing the selected modulation and coding.
 9. A method for transmittingdata in a communications system, the method comprising: transmittingscheduling information specifying resources on which the data are to betransmitted and including a modulation and coding indicator; selectingmodulation and coding from a set of predefined modulation and codingschemes according to the modulation and coding indicator, selecting theset of predefined modulation and coding schemes from at least twopredefined sets—the first set and the second set, which have a pluralityof modulation and coding schemes in common and differ in that the secondset further includes an additional modulation with an order higher thanany modulation in the first set, and the first set and the second sethave the same size; and receiving the data on the scheduled resourcesusing the selected modulation and coding.
 10. The method according toclaim 8, wherein the modulation and coding schemes in each of the setsare associated with the values of modulation and coding indicator, aplurality of the modulation and coding indicator values refer to therespective same modulation and coding schemes in the first and in thesecond set, and the remaining modulation and coding indicator valuesrefer in the second set to the highest-order modulation and in the firstset to modulation(s) of one or more lowest order(s).
 11. The methodaccording to claim 8, wherein M lowest values of the modulation andcoding indicator, M being an integer, refer to: the modulation andcoding schemes with the lowest-order modulation in the first set, andthe modulation and coding schemes with the highest-order modulation inthe second set.
 12. The apparatus according to claim 8, wherein thesecond set does not include modulation with the lowest order included inthe first set.
 13. The apparatus according to claim 8, wherein: K valuesof the modulation and coding indicator, K being an integer, refer to thesame modulation and coding schemes with the lowest-order modulation inboth the first and the second set, L values refer to the modulation andcoding schemes with the lowest-order modulation in the first set and themodulation and coding schemes with the highest-order modulation in thesecond set, and the remaining values of the modulation and codingindicator refer to the same modulation and coding schemes lower than thehighest-order modulation.
 14. The method according to claim 8, whereinthe modulation and coding indicator is associated with a modulation andcoding scheme including: a modulation order and a size indicatorindicating at least one of (i) the number of bits in a transport blockwhich is to be mapped onto physical resources and (ii) retransmissionwithout specific indication of the transport block size.
 15. The methodaccording to claim 8, wherein: the choice of the set is performed by anetwork node, signaled to a terminal, and the selection of the set atthe terminal is performed accordingly, wherein the signaling is ahigher-layer signaling less frequent than the signaling of themodulation and coding indicator, or the choice of the set is performedby a network node, signaled to a terminal, and the selection of the setat the terminal is performed accordingly, wherein the signaling iscarried on the same layer as the signaling of the modulation and codingindicator, but less frequently, or the selection of the set is performedby both a terminal and a network node based on the terminal's channelconditions reported from the terminal to the network node.